1. Technical Field
The present invention is directed to a digital processing apparatus, more specifically to a digital processing apparatus having a plurality of processors.
2. Description of the Related Art
A portable terminal refers to a compact electronic device that is designed to be easily carried by a user in order to perform functions such as game or mobile communication. A portable terminal can be a mobile communication terminal, a personal digital assistant (PDA) or a portable multimedia player (PMP).
The mobile communication terminal is essentially a device designed to enable a mobile user to telecommunicate with a receiver who is remotely located. Thanks to scientific development, however, the latest mobile communication terminals have functions, such as camera and multimedia data playback, in addition to the basic functions, such as voice communication, short message service and address book.
FIG. 1 shows a block diagram of a conventional mobile communication terminal having a camera function.
Referring to FIG. 1, the mobile communication terminal 100 having a camera function comprises a high frequency processing unit 110, an analog-to-digital converter 115, a digital-to-analog converter 120, a processing unit 125, a power supply 130, a key input 135, a main memory 140, a display 145, a camera 150, an image processing unit 155 and a support memory 160.
The high frequency processing unit 110 processes a high frequency signal, which is transmitted or received through an antenna.
The analog-to-digital converter 115 converts an analog signal, outputted from the high frequency processing unit 110, to a digital signal and sends to the processing unit 125.
The digital-to-analog converter 120 converts a digital signal, outputted from the processing unit 125, to an analog signal and sends to the high frequency processing unit 110.
The processing unit 125 controls the general operation of the mobile communication terminal 100. The processing unit 125 can comprise a central processing unit (CPU) or a micro-controller.
The power supply 130 supplies electric power required for operating the mobile communication terminal 100. The power supply 130 can be coupled to, for example, an external power source or a battery.
The key input 135 generates key data for, for example, setting various functions or dialing of the mobile communication terminal 100 and sends the key data to the processing unit 125.
The main memory 140 stores an operating system and a variety of data of the mobile communication terminal 100. The main memory 140 can be, for example, a flash memory or an EEPROM (Electrically Erasable Programmable Read Only Memory).
The display 145 displays the operation status of the mobile communication terminal 100 and an external image photographed by the camera 150.
The camera 150 photographs an external image (a photographic subject), and the image processing unit 155 processes the external image photographed by the camera 150. The image processing unit 155 can perform functions such as color interpolation, gamma correction, image quality correction and JPEG encoding. The support memory 160 stores the external image processed by the image processing unit 155.
As described above, the mobile communication terminal 100 having a camera function is equipped with a plurality of processors. The plurality of processors can comprise a main processor and one or more application processors, which are controlled by the main processor and perform predetermined additional functions. In other words, as shown in FIG. 1, the processing unit 125 for controlling general functions of the mobile communication terminal 100 and the image processing unit 155 for controlling the camera function are included. The operations of the application processors for additional functions can be controlled by the main processor. Moreover, each processing unit is structured to be coupled with an independent memory.
The application processor can take different forms depending on the kinds of additional functions, with which the portable terminal is equipped. For example, the application processor for controlling the camera function can process functions such as JPEG encoding and JPEG decoding; the application processor for controlling the movie file playback function can process functions such as video file (e.g., MPEG4, DIVX, H.264) encoding and decoding; and the application processor for controlling the music file playback function can process functions such as audio file encoding and decoding. Of course, there can be an application processor that can process various aforementioned functions altogether. Each of these processing units has an individual memory for storing the data processed by the processing unit. Therefore, according to the related art, it is necessary to increase the number of processing units and memories as portable terminals become increasingly multifunctional.
FIG. 2 illustrates an example of a coupling structure among a main processor, an application processor and their corresponding memories in accordance with the related art.
Referring to FIG. 2, the main processor 210 and the application processor 220 communicate information through a host interface; the main processor 210 is coupled to the main memory 230 through an MP (main processor)-MM (main memory) bus; and the application processor 220 is coupled to the supplementary memory 240 through an AP (application processor)-AM (application memory) bus. A bus refers to a common-purpose electric pathway that is used to transmit information between the processor, the main memory and the input/output in a device such as a computer. A bus comprises a line for data, designating the address of each device or the location of the memory, and a line for distinguishing a variety of data transmission operation to be processed.
As illustrated in FIG. 2, each of the processors 210 and 220 is independently coupled to each of the memories 230 and 240.
Depending on the operation that is currently running, the main processor 210 reads data stored in the main memory 230 and transmits the data to the application processor 220 through the host interface or receives data stored in the supplementary memory 240 by requesting the application processor 220.
In other words, in case a certain process operation is to be processed in the main processor 210 and the application processor 220, respectively, in order to process certain data, the main processor 210 first accesses the main memory 230 to perform a necessary operation and then transmits the processed data to the application processor 220, and the application processor 220 re-processes the received data and stores the data in the supplementary memory 240. Then, the application processor 220 transmits the data stored in the supplementary memory 240 back to the main processor 210 to have it stored in the main memory 230.
In this case, the larger the amount of data is communicated between the main processor 210 and the application processor 220, the more time each of the processors 210 and 220 has to spend on the operation (i.e. memory access, host interface operation) requested by the other processor rather than the operation of its own process.
This problem causes a bottleneck in data communication between the main processor 210 and the application processor 220 as the amount of data to be processed and the functions performed by the portable terminal increase.
As a result, the problems described above weaken the overall performance of a multi-function portable terminal.